3 Requirements
3.1 Architectural requirements
The developing concept and VCA modules should be implemented in accordance with requirements to the modules of OpenSCADA system. The developed conceptual mechanism should contain all the algorithms and data which are shared by VCA, built on different principles, but also contain the mechanism for the visualization interface sessions' execution. In fact, the realizations of VCA it must be formed the individual visualization(rendering) mechanisms and mechanisms of interaction with the user, based on this concept, ie to form the individual interface of visualization of data of the VCA concept in accordance with the ideology of "Model/data - Interface".
3.2 General requirements
Visualization should include the following functions:
- Showing the operational and archival information of TP in numeric, graphic (in the form of the mimic of the TP, time diagrams) forms.
- Alarms on violations of TP by color, flashing of the background, lines, text, the list of violations in tabular form.
- Provision of archived reports of violations of TP, activities of the operator and system operations. Messages must be displayed using different kinds of filters: by category, date/time.
Control of the technological equipment and the parameters of TP must provide the following functions:
- Remote control of discrete actuating mechanisms, the working modes.
- Input by the operator the analog values.
- Confirmation of the operator's commands' execution, recording the action of the operator in the messages subsystem, as well as rights politics of the commands' execution.
The commands of the operator to control TP and navigation within the subsystem must be made using the keyboard and mouse or other input device.
As input data, the implementations of the VCA must use the data from the following subsystems of OpenSCADA:
- Subsystem "Data acquisition (DAQ)" to obtain the list of parameters, their attributes, values and history of changes of επσ attribute's values.
- Subsystem "Archives" to obtain and visualize archives (history) of values and messages.
- Subsystem "Security" to obtain the list of users and access control.
- Subsystem "DB" to store and retrieve configuration of VCA.
The output data of the VCA realization:
- Image on the display.
- Modified by the operator current values of TP (for example, mode of the PID regulator, set-point of the regulator, output of the regulator, regulator's settings, remote equipment control, etc.), coming into the subsystem "DAQ".
- Reporting documentation in the form of various protocols, reports and documents.
Configuration of VCA must be store in the accessible to the OpenSCADA system databases, allowing thus to choose one or another database for the specific practical situation. Images and other resources are to be encoded by Mime Base64 algorithm and stored in the database.
Update cycle of the operational information on the screen depends on the specific VCA implementation. For fast visualization interfaces this cycle should not exceed 1 second.
3.3 Reliability requirements
Ensuring for reliable operation and protection from the unauthorized access to the VCA should be implemented at several levels:
- At the level of the OpenSCADA core.
- At the level of the VCA concept. For each element of the display should be done it's own rights policy for the editing (Development mode), the dynamics and responding to events (Runtime mode) by means of the ownership change (using the functions of the subsystem "Security"), inclusion/exclusion into/from the group and change rights to modify, read and execute respectively.
- At the level of the single VCA implementation with the generic concept usage.
Implementation of the VCA, in conjunction with the concept, must meet the following requirements for reliability:
- Continuous operation 24 hours a day, 360 days a year.
- The maximum recovery time of working status - no more than 1 h.
- Error detection (no frame, exceptional circumstances) their correct processing and delivery of relevant messages.